[HELICONIUS] Four new papers on Heliconius

[James Mallet]

...including the description by Mérot et al. of the new timareta from 
Peru, /thelxinoe/!

Supple MA, Hines HM, Dasmahapatra KK, Nielsen DM, Lavoie C, Ray DA, 
Salazar C, McMillan WO, Counterman BA. 2013. Genomic architecture of 
adaptive color pattern divergence and convergence in  Heliconius 
butterflies. Genome Research (online pre-publication)

Identifying the genetic changes responsible for adaptive variation in 
natural populations is keyto understanding how biodiversity is 
generated. The mosaic of mimetic wing patterns inHeliconius butterflies 
makes them an excellent system for exploring the origins of adaptive 
variation using next-generation sequencing techniques. In this study, we 
use RNA-Seq toannotate the genomic interval modulating red color pattern 
variation and whole genomeresequencing of multiple color morphs to 
identify a narrow region responsible for adaptivedivergence and 
convergence in Heliconius wing patterns. Using population and 
phylogeneticanalyses across four hybrid zones between color morphs of H. 
erato and two hybrid zones ofthe co-mimic H. melpomene, we identify a 
shared 65 kb island of divergence in the intergenicregion near optix, 
the gene which was previously shown to be responsible for the complex 
redpattern variation in Heliconius. Our dense SNP analysis reveals 
several sites in this region perfectly associated with red color pattern 
phenotype in both species. This region likely contains multiple 
cis-regulatory elements that control discrete expression domains of 
optix.The parallel signatures of genetic differentiation in H. erato and 
H. melpomene support ashared regulatory architecture between the two 
distantly related co-mimics; however,phylogenetic analyses and the 
absence of shared candidate SNPs suggest mimetic patterns ineach species 
evolved independently. Using a combination of next-generation 
sequencingtechniques, we have refined our understanding of the genetic 
architecture of wing patternvariation in Heliconius and gained important 
insights into the evolution of novel adaptivephenotypes in natural 
populations.


Mérot C, Mavárez J, Evin A, Dasmahapatra KK, Mallet J, Lamas G, Joron M. 
2013. Genetic differentiation without mimicry shift in a pair of 
hybridizing Heliconius species (Lepidoptera: Nymphalidae). Biological 
Journal of the Linnean Society (online early).

Abstract: Mimetic butterflies in the genus Heliconius have undergone 
rapid adaptive radiation for warning patterns, and are excellent models 
to study the mechanisms underlying diversification. In Heliconius, 
mimicry rings typically involve distantly-related species, while closely 
related species often join different mimicry rings. Genetic and 
behavioural studies have shown how a reduction of gene flow in 
Heliconius is often mediated, in part, by natural and sexual selection 
on wing colour pattern. However, recent studies have uncovered new cases 
in which pairs of closely-related species are near-perfect mimics of 
each other. Here, we provide morphometrical and genetic evidence for the 
coexistence of two very closely related, hybridizing co-mimics on the 
eastern Andean foothills, H. melpomene amaryllis and H. timareta ssp. 
nov., which is described here as *H. t. thelxinoe*. A joint analysis of 
multilocus genotyping and geometric morphometrics of wing shape shows a 
high level of differentiation between the two species with only limited 
gene flow and mixing. Some degree of mixing can be detected, although 
putative hybrids were rare (one out of 175 specimens was a clear 
hybrid). In contrast, we found phenotypic differentiation between 
populations of H. timareta thelxinoe, possibly indicative of strong 
selection for local mimicry in different communities. In this pair of 
species where promiscuous exchange of wing patterning alleles has been 
demonstrated, the absence of breakdown of genetic isolation when wing 
pattern are similar implies that factors other than wing patterns keep 
the two taxa separate, such as chemical or behavioural signals, or 
ecological adaptation along a strong altitudinal gradient.


Cardoso MZ, Gilbert LE. 2013. Pollen feeding, resource allocation and 
the evolution of chemical defence in passion vine butterflies. Journal 
of Evolutionary Biology (online early).

Abstract: Evolution of pollen feeding in Heliconius has allowed 
exploitation of rich amino acid sources and dramatically reorganized 
life-history traits. In Heliconius, eggs are produced mainly from 
adult-acquired resources, leaving somatic development and maintenance to 
larva effort. This innovation may also have spurred evolution of 
chemical defence via amino acid-derived cyanogenic glycosides. In 
contrast, nonpollen-feeding heliconiines must rely almost exclusively on 
larval-acquired resources for both reproduction and defence. We tested 
whether adult amino acid intake has an immediate influence on 
cyanogenesis in Heliconius. Because Heliconius are more distasteful to 
bird predators than close relatives that do not utilize pollen, we also 
compared cyanogenesis due to larval input across Heliconius species and 
nonpollen-feeding relatives. Except for one species, we found that 
varying the amino acid diet of an adult Heliconius has negligible effect 
on its cyanide concentration. Adults denied amino acids showed no 
decrease in cyanide and no adults showed cyanide increase when fed amino 
acids. Yet, pollen-feeding butterflies were capable of producing more 
defence than nonpollen-feeding relatives and differences were detectable 
in freshly emerged adults, before input of adult resources. Our data 
points to a larger role of larval input in adult chemical defence. This 
coupled with the compartmentalization of adult nutrition to reproduction 
and longevity suggests that one evolutionary consequence of pollen 
feeding, shifting the burden of reproduction to adults, is to allow the 
evolution of greater allocation of host plant amino acids to defensive 
compounds by larvae

Hill RI, Gilbert LE, Kronforst MR. 2013. Cryptic genetic and wing 
pattern diversity in a mimetic Heliconius butterfly. Molecular Ecology 
(online early).

Abstract: Despite rampant colour pattern diversity in South America, 
Heliconius erato exhibits a "postman" wing pattern throughout most of 
Central America. We examined genetic variation across the range of H. 
erato, including dense sampling in Central America, and discovered a 
deep genetic break, centred on the mountain range that runs through 
Costa Rica. This break is characterized by a novel mitochondrial 
lineage, which is nearly fixed in northern Central America, that 
branches basal to all previously described mitochondrial diversity in 
the species. Strong genetic differentiation also appears in Z-linked and 
autosomal markers, and it is further associated with a distinct, but 
subtle, shift in wing pattern phenotype. Comparison of clines in wing 
phenotype, mtDNA and nuclear markers indicate they are all centred on 
the mountains dividing Costa Rica, but that cline width differs among 
data sets. Phylogeographical analyses, accounting for this new 
diversity, rewrite our understanding of mimicry evolution in this 
system. For instance, these results suggest that H. erato originated 
west of the Andes, perhaps in Central America, and as many as 1 million 
years before its co-mimic, H. melpomene. Overall our data indicate that 
neutral genetic markers and colour pattern loci are congruent and 
converge on the same hypothesis. H. erato originated in northwest South 
America or Central America with a "postman" phenotype and then radiated 
into the wealth of colour patterns present today

-- 
James Mallet
OEB & GEE Depts
Harvard University & University College London
Cambridge, MA 02138 and LONDON WC1E 6BT
USA tel: +(1)617-496-5350
www.ucl.ac.uk/taxome/jim

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